1. Field of the Invention
The present invention relates to an optical transmission apparatus and, more particularly, to an optical transmission apparatus including a cooler for controlling the temperature of the optical transmission apparatus.
2. Description of the Related Art
A WDM-PON (Wavelength Division Multiplexing Passive Optical Network) technique using WDM is a communication technique capable of grouping optical signals of different wavelengths by using a single optical fiber and transmitting the same.
The WDM-PON technique has advantages in that it does not cause interference with an optical signal of a different wavelength, guarantees a broadband bi-directional symmetrical service by assigning a unique wavelength to each subscriber, and has excellent security because only a particular subscriber is allowed to receive an optical signal of a particular wavelength. The WDM technique has been commonly used in the existing backbone network and, recently, there is a move to extend the use of the SDM technique even to a subscriber network.
In case of optical communication using WDM, because it uses the method of dividing wavelength, compared with existing time division multiplexing and frequency division multiplexing, it requires a thermo-electric cooler for controlling an operational temperature of a light source to have a certain degree in order to ensure temperature stability of an optical module, namely, in order to prevent malfunctions caused by a wavelength transition according to temperature.
However, the installation of the cooler in an optical transmission apparatus increases the size of an optical transmission module, which may in turn trigger secondary problems.
For example, when a package, a cooler, a substrate, various elements (e.g., a light source, a monitoring element, a reflector, a thermister, and the like), are sequentially stacked, the distance between the package and the elements is increased due to the presence of the cooler. Then, a lead pin of the package for supplying the power of the elements, a bonding wire for connecting the package lead pin and the elements would be lengthened and the signal transmission characteristics of the optical transmission apparatus would deteriorate proportionally. In addition, a cooling load of the cooler increased according to the size of the optical transmission module.